Purification and clarification of water.



UNITED STATES PATENT OFFICE.

WILLIAM MCMURTRIE, OF NEW YORK, N. Y.

PURIFICATION AND CLARIFICATION OF WATER.

York, in the county of New York and State of New York, have invented certain new and useful Improvements in Purification and Clarification of Water, of which the followin is a specification.

his invention relates to the purification and clarification of Water and has particular reference to an improved rocess of removing finely divided suspen ed matter therefrom by producin therein an insoluble precipitate which wil mechanically carry such matter down in sedimentation, or hold it back in filtration.

The invention has for its particular object,

to provide a process which will be at once more efficient and less expensive than roc- 20 esses of purifying water which have een heretofore employed and which will avoid in the practice thereof, the roduction of gelatinous and slimy masses W ich interfere with filtration and sedimentation.

A further object of my invention is to provide a process which will free water from scale forming constituents and bacterial contammat1ons, and which will afford a residue or sludge, which will be a valuable fertilizer.

H eretofore tri-calcium phosphate has been utihzed ingthe purification of sugar and other solutions but, it has been found in practice thatthis salt will not alone effect the satisfactory precipitation of finely dividedsuspended matter, even after lon standing. The process is also 0 on to the urther objection that the resi ue or sludge contains the phosphate added-in the form of tri-calcium phosphate, which is inefiicient as a fer- Other attempts have been made to effect the purification of liquids by the employment of tri-calcium phos hates, but none of them{ has been found tofge capable of being suocessfu yemployed in the PUIifiCZLtlOII of Water; 'J';:.'.' f

I have discovered that I can satisfactorily accompli h the objects'of my invention by utilizingra dii-calciumphosphate in place of v a tri-basicphosphate and .th'aitby such use of a di-basmrphbspfh te{ev n case of Specification of Letters Patent.

Application filed May 29, 1908.

:When' calcium or magnesium Patented Feb. 23, 1909.

Serial No. 435,851.

the lighter di-basic phosphates, as for example, di-caleium phosphate, I am able to effect the rapid and satisfactory urification of water and sewage without t e'employment of diatomaceous earth, or any other auxiliary filtering agent to assist in the removal of finely dlvided suspended matter.

In the ractice of my process, in its preferred embodiment, I add to the water to be treated, a predetermined quantity of acid calcium hosphate, and when this has been thorouglily mixed with the water, ifsaid water be free from salts of calcium and magnesium, I add thereto, a predetermined quantity of a basic substance, as for example, calcium, sodium or potassium hydroxid, or sodium or potassium carbonate. The reagents are so proportioned that the acid calcium phosphate will, in all cases, combine with all of the basic substance employed and will form therewith a di-basic phosphate. If an excess of the basic substance is present, tricalcium phosphate will be formed WhlCll Wlll interfere with the successful purification and clarification of the water in accordance with my process. If the water under treatment contains a sufficient quantity of soluble alkaline carbonates to produce, with the. acid calcium hosphate added, a di-calcium phosphate, then theuse of an additional basic substance is unnecessary and is to be avoided. Inall cases, the mineral impurities of the water are to be determined and the reagents employed to effect the. purification o the water added in such proportions that there will be no excess of basic-materials and the product of the reaction will be a di-basic phosphate.

The following equation shows the roportions in which the reagents are or employed:

OaH,(PO,) 2 Ca (OH) Ca H,(PO,) 2 2H O When alkaline bases other than lime are used'such for example, as caustic soda, the following equation indicates the proportions of the reagents. v '2oa ,(Po.).+4NaoH= inarily I 051 114130, zn nro, j+ 4H,.o,-, I

present in the water, the following equations indicate the proportions of the reagents required to produce the desired result:

ZNa HPO, 2CaCl Ca,H,(PO 2 lNaCl 2Na HPO 2MgCl Mg H (P0,) 2 4NaCl When the acid calcium phosphate or such hosphate and one or more basic materials liave been added, there is produced within the water, a precipitate of di-calcium phosphate which, rapidly becoming crystalline, attaches itself to the suspended particles in the water and carries them down in sedimentation or holds them back in filtration. This makes it possible to separate the suspended solids by either sedimentation or filtration as preferred, and in case the process is applied to such turbid waters as sewage, it yields as a recipitate or sludge, a product which has a liigh agricultural value as fertilizer, because the organic matters contained in the liquid treated are separated out, and the di-basic phosphate itself is a very valuable plant food.

When the water contains sca e forming constituents, other than carbonates, such as the chlorids or sulfates, I prefer to add to the water either before or after the addition of the phosphate, sodium or potassium carbonate. By this means such double decompositions ensue that the magnesium and calcium are removed from the water as di-basic phosphates.

The process may be successfully applied to the disposal of sewage. In this use of the process, the sewage is impounded and mixed with the necessary quantity of acid calcium phosphate alone, or mixed with a basic substance as milk of lime. To secure the most effective admixture of the acid calcium phosphate, it is charged into the sewer some distance from its outlet and, at a point nearer the outlet, milk of lime is added in the necessary quantity. Di-calcium phosphate is thus roduced and when the sewage is impoun ed at the mouth of the sewer, sedimentation proceeds promptly with the separation of al suspended matter, the remaining liquid being a relatively clear efliuent. If desired, the sewage may be filtered to secure more effectively a clear efliuent. In either case, the sediment or sludge can be fully collected, preserved, dried, and used for fertilizer. It will contain in the form of di-basic phosphate, all of the phosphate added to the sewage. It will also contain all of the organic matters suspended in the sewage and a considerable portlon of the soluble nitrogenous -substances contained therein. It is thus possible by my rocess, to recover for use as fertilizer, practically all of the sewage waste of cities together with all the phosphates used in the process.

I have found that some measure of success may be attained by the substitution of phosphoric acid or a mixture of such acid with acid calcium phosphate for the acid calcium phosphate hereinbefore referred to, in roportions to roduce di-calcium phosp ate with the baslc calcium salts present in the water, or added thereto as described. It will be evident however, that when phosphoric acid, or such acid together with acid calcium phosphate is used, a greater amount of lime is re uired to produce the di-calcium phosphate t an when acid calcium phosphate alone is em loyed.

Having fully escribed my invention, 1 claim:

1. A process of clarifying andpurifying Water, which consists in causing a predetermined quantity of a reagent contaming the phosphate radical to react in the presence of said water, with a basic substance adapted to form therewith a preci itate of phosphate in soluble in water, the phosphate radical being addedin such proportions as to combine with all of said basic substance, and to form therewith a di-basic hosphate.

2. A process of clarifying and purifying water, which consists in causing a predetermined quantity of an acid phosphate to react in the presence of said water, with a basic substance adapted to form therewith aprecipitate insoluble in water, the phosphate being added in such proportions as to combine Y with all of said basic substance, and to form therewith a di-basic phosphate. .7

' 3. A process of clarifylng and purifying water, which consists in causing a predetermined quantity of acid calcium phosphate to react in the presence of said water, with a basic substance adapted to form therewith a precipitate insoluble in water, the phosphate being addedin such proportions as to com bine with all the said basic substance and to form therewith a di-basic hosphate.

4. A- rocess of clarifylng and purifying water W ich consists in adding thereto in a selected order of succession, a redeter mined quantity of acid calcium osphate and a corres bnding predetermined quantity of a basic su stance, the said reagents being employed in proportion to roduce, by their reaction, apreciplt'ate of a d1-basic hosphate. 5. A rocess of clarifying an purifying water, w ich consists in mixing therewith a predetermined quantity of acid calcium phosphate, then adding a predetermined quantity of a basic substance, the said reagepts being added in proportions to produce a precipitate of di-calcium phosphate.

"6. A process of clarifying and purifying water, which consists in causing a predetermined quantity of acid calcium phosphate to react in the presence "of said water with a basic substance adapted to form therewith a precipitate insoluble in water, the phosphate 1 eing added in such roportions as to combine with all of said asic substance and to form therewith a di-basic phosphate, said 5 basic substance having a molecular weight not in excess of that of the corresponding compound of calcium.

7. A rocess of clarifying and purifying water, which consists in successively adding 10 thereto a predetermined quantity of acid calciumphosphate and a corresponding predetermined quantity of a basic substance, the said reagents being employed in proportions to produce, by their reaction, a precipitate of a di-basic phosphate, the said basic subla stance having a molecular Weight not in excess of that of the corresponding'oompound of calcium.

' WILLIAM MOMURTRIE.

Witnesses:

a J. F. CHUMASEROF EVAN S. SHERLOCK. 

